1. Field of the Invention
The present invention relates to a color ink jet recording method capable of recording a clear, high-density color image and, more particularly, to a color ink jet recording method using color inks such as yellow (Y), magenta (M), and cyan (C) inks, or green (G), red (R), and blue (B) inks, together with a black (Bk) ink.
The present invention can be applied to all apparatuses using recording media such as paper, a cloth, a non-woven fabric, an OHP sheet, and the like, and the apparatuses to which the present invention is applied include a printer, a copying machine, a facsimile apparatus, and the like.
2. Related Background Art
An ink jet recording method is utilized in a printer, a copying machine, a facsimile apparatus, and the like due to its advantageous features, i.e., low noise, low running cost, easy realization of a compact apparatus and a color arrangement, and the like.
In general, a color ink jet recording method performs color recording using three color inks, i.e., C, M, and Y inks, or four color inks obtained by adding Bk to the above-mentioned three inks.
In a conventional ink jet recording method, in order to obtain a highly color-developed color image free from ink blurring, a special-purpose paper sheet having an ink absorbing layer must be used. However, in recent years, a method with printing adaptability to "normal paper sheets", which are used in large amounts in a printer, a copying machine, and the like, due to improvement of inks has been put into practical applications. However, printing quality on "normal paper sheets" does not have a satisfactory level yet. The most serious cause of such low printing quality is a conflict between 1 blurring of different color inks and 2 black recording quality (in particular, black character recording quality).
Normally, when a color image is obtained on a normal paper sheet by the ink jet recording method, quick-drying inks which have a high penetration speed to normal paper sheets are used. For this reason, a high-quality image, which is free from blurring of different color inks, can be obtained. However, the entire image has a low density, and so-called feathering in which inks slightly blur along fibers of paper tends to occur around recorded image areas of the respective colors.
Feathering is not relatively conspicuous in a color image area, but is conspicuous in a black image area, thus deteriorating recording quality. In particular, when a black image is a character, an unclear character having no sharpness is formed, and its quality is poor.
In order to achieve high-quality black color recording which is free from feathering and has a high density, a black ink having a relatively low penetration speed to a normal paper sheet must be used. However, in this case, different color inks blur at a boundary portion between adjacent recorded image areas of black and another color, thus considerably deteriorating image quality.
In this manner, improvement of color recording quality by achieving both prevention of blurring of different color inks, e.g., a black ink and another color ink, and elimination of feathering of, especially, black poses conflicting problems.
Japanese Laid-Open Patent Application No. 3-146355 proposes a method in which no image is recorded on an area along a boundary between black and another color. However, with this method, data to be recorded may change.
Also, Japanese Laid-Open Patent Application No. 4-158049 proposes a method in which a plurality of color heads for color recording, and a character recording head are arranged, and the plurality of color heads and the character recording heads are selectively used in correspondence with an image to be recorded. However, with this method, an apparatus must have the character recording head in addition to the plurality of color heads for conventional color recording, resulting in increases in cost and in apparatus scale.
On the other hand, a problem about blurring of inks can be solved to some extent by a recording mode (to be referred to as a fine mode hereinafter) for divisionally forming an image in a plurality of number of times of main scans. However, the above-mentioned problem about black image quality remains unsolved essentially.